1. Technical Field
This disclosure is generally related to oscillators, which may, for example, be employed in power converters and other devices.
2. Description of the Related Art
Power converters are used to transform electrical energy, for example converting between alternating current (AC) and direct current (DC), adjusting (e.g., stepping up, stepping down) voltage levels and/or frequency.
Power converters take a large variety of forms. One of the most common forms is the switched-mode power converter or supply. Switched-mode power converters employ a switching regulator to efficiently convert voltage or current characteristics of electrical power. Switched-mode power converters typically employ a storage component (e.g., inductor, transformer, capacitor) and a switch that quickly switches between full ON and full OFF states, minimizing losses. Voltage regulation may be achieved by varying the ratio of ON to OFF time or duty cycle. Various topologies for switched-mode power converters are well known in the art including non-isolated and isolated topologies, for example boost converters, buck converters, synchronous buck converters, buck-boost converters, and fly-back converters.
In the interest of efficiency, digital logic technology is employing ever lower voltage logic levels. This requires power converters to deliver the lower voltages at higher currents level. To meet this requirement, power converters are employing more energy efficient designs. Power converters are also increasingly being located in close proximity to the load in as point of load (POL) converters in a POL scheme. These power converters must generate very low voltage or potential levels (e.g., less than 1V) at increasingly higher current levels (e.g., greater than 10 A). These relatively high current levels may be difficult to achieve with a single power converter.
Manufacturers are also increasingly employing POL schemes in light of the widely varying voltage requirements in modern systems (e.g., computer systems). A POL scheme may be easier to design and/or fabricate, take up less area, and/or produce less interference than employing multiple different power buses. The POL schemes typically employ one or two power buses with a number of POL regulators located close to specific components or subsystems to be powered, for example microprocessors, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), volatile memory. The POL regulators adjust voltage or potential to supply localized busses feeding the specific components or subsystems.
Switched mode power converters typically include an oscillator or oscillator circuit which generates, provides or supplies a periodic, oscillating ramp voltage waveform to a gate timing and drive control for use in generating pulse width modulated control signals for controlling one or more switches of the converter circuit. It is desirable that the oscillator provide a linear ramp signal with ramp voltage rate of change (dv/dt) rate proportional to the supply input voltage while maintaining a fixed frequency over a wide range of frequencies and over a wide range of temperatures. Additionally, the oscillator may need to be synchronized with other oscillating waveforms and other frequencies, for example those from a system clock or another power converter. Further, it is typically desirable that the oscillator is relatively inexpensive to manufacture.
New approaches to related to oscillation circuits are desirable.